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Ebola Virus Disease

Ebola Virus Disease

26 May 2017

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Causative agent

The Ebola virus disease (EVD; formerly known as Ebola haemorrhagic fever) is caused by infection with Ebola virus which belongs to the family called Filoviridae. EVD in humans has an average case fatality rate of around 50% (varied from 25% to 90% from previous outbreaks).

Ebola first appeared in 1976 in South Sudan and the Democratic Republic of Congo, the latter in a village situated near the Ebola River, from which the disease took its name. The disease has appeared sporadically since then. Confirmed cases of EVD have been reported in sub-Saharan Africa including the Democratic Republic of the Congo, Gabon, South Sudan, Cote D'Ivoire, Uganda, and Congo. 

The Ebola virus outbreak occurred in West Africa since March 2014 is the largest outbreak since the Ebola virus was first discovered in 1976. It affects mainly Guinea, Liberia and Sierra Leone. All known chains of transmission of the outbreak have been stopped in West Africa and the main epidemic came to an end in January 2016. However, several new flare-ups have been reported since then. 

Clinical features

EVD is a severe acute viral illness often characterised by the sudden onset of fever, intense weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhoea, rash, impaired kidney and liver function, and in some cases, both internal and external bleeding.

Mode of transmission

Ebola virus is introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals. Some fruit bats are considered to be the natural host of the Ebola virus. In Africa, infection has been documented through the handling of infected chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead in the rainforest.

It then spreads in the community through human-to-human transmission, with infection resulting from direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and indirect contact with environments contaminated with such fluids.

People are infectious as long as their blood and secretions contain the virus. Burial ceremonies in which mourners have direct contact with the body of the deceased person can also play a role in the transmission of Ebola. Healthcare workers in affected countries have frequently been infected through close contact with patients suffering from EVD when infection control measures are not strictly practised. Samples from patients are biohazardous and testing should be conducted under appropriate biological containment conditions.

Although rare, sexual transmission of Ebola virus has been reported. Based on present evidence, World Health Organization recommends that survivors of EVD and their sexual partners should either abstain from all types of sex, or practise safe sex through correct and consistent condom use for 12 months from onset of symptoms or until the semen tests negative twice for Ebola virus.

Incubation period

It ranges from 2 to 21 days.


There is no specific treatment for the disease.

Patients must be managed in isolation facilities to prevent the spread of the infection. Severely ill patients require intensive supportive care. Patients are frequently dehydrated and require oral or intravenous rehydration. 

Healthcare workers should put on protective gears and adopt strict infection control measures when caring for suspected patient.


There is no licensed vaccine to prevent EVD yet. An Ebola vaccine, called rVSV-ZEBOV, was shown to be highly protective against the deadly virus in a major trial led by World Health Organization in Guinea in 2015.

To prevent the infection, it is important for the travellers to observe the following:

  • Observe good personal and environmental hygiene, always remember to use liquid soap or alcohol-based handrub to clean your hands before touching the eyes, nose and mouth
  • Avoid close contact with feverish or ill persons, and avoid contact with blood or bodily fluids of patients, including items which may have come in contact with an infected person's blood or bodily fluids
  • Avoid contact with animals
  • Cook food thoroughly before consumption

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